Conventionally, a communication scheme called MIMO (Multiple-Input Multiple-Output) has been for example used as a multi-antenna communication method.
According to multi-antenna communication method as typified by the MIMO, transmission data of one or more sequences is modulated, and modulated signals are transmitted from different antennas at the same time at the same (shared/common) frequency. This increases data reception quality and/or increases the data transfer rate (per unit time).
FIG. 72 illustrates an outline of a spatial multiplexing MIMO scheme. The MIMO scheme in the figure shows an example of configuration of a transmission device and a reception device in the case where two transmission antennas TX1 and TX2, two reception antennas RX1 and RX2, and two transmission modulated signals (transmission streams) are used.
The transmission device includes a signal generator and a wireless processing unit.
The signal generator performs channel coding on data and MIMO precoding process on the data, and thereby generates two transmission signals z1(t) and z2(t) that are transmittable at the same time at the same (shared/common) frequency. The wireless processing unit multiplexes transmission signals in the frequency domain as necessary, in other words, performs multicarrier processing on the transmission signals (by an OFDM scheme for example). Also, the wireless processing unit inserts pilot signals for the reception device to estimate channel distortion, frequency offset, phase distortion, and so on. (Note that the pilot signals may be inserted for estimation of other distortion and so on, and alternatively the pilot signals may be used by the reception device for detection of signals. The use case of the pilot signals in the reception device is not limited to these.) The two transmission antennas TX1 and TX2 transmit the transmission signals z1(t) and z2(t), respectively.
The reception device includes the reception antennas RX1 and RX2, a wireless processing unit, a channel variation estimator, and a signal processing unit. The reception antenna RX1 receives the transmitted signals which are transmitted from the two transmission antennas TX1 and TX2. The channel variation estimator estimates channel variation values using the pilot signals, and transfers the estimated channel variation values to the signal processing unit. The signal processing unit restores data included in the transmission signals z1(t) and z2(t) based on the signals received by the two reception antennas and the estimated channel variation value, and thereby obtains a single piece of reception data. Note that the reception data may have a hard-decision value of 0 or 1, and alternatively may have a soft-decision value such as a log-likelihood and a log-likelihood ratio.
Also, various types of coding schemes have been used such as turbo coding and LDPC (Low-Density Parity-Check) coding (Non-Patent Literature 1 and Non-Patent Literature 2).